Control device



Jam 1950 c. a. KRONMILLER 2,

CONTROL DEVICE Filed July 5, 1946 3nnentor C/ML G. IfliO/VMILLE/f Gttomeg Patented Jan. 3, 1950 UNITED STATES PATENT ornca CONTROL DEVICE Carl G. Kronmiller, Edlna, Minn., asslgnor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application July 5, 1946, Serial No. 681,461

6 Claims. (Cl. 200-139) This invention relates to condition responsive control devices and more particularly to a control device for controlling heat varying means to maintain the temperature of a room or the like at a predetermined selected value.

An object of the invention is to provide a novel snap acting electric switching mechanism.

Another object of the invention is to provide a temperature responsive control device in which the temperature responsive element and the switching mechanism are independently mounted on a base.

Another object is to provide a magnetic snap acting switching mechanism including a resilient blade serving the dual purpose of pivotally supporting a combined actuating member and armature and acting as a resilient contact carrying blade.

Another object is to provide such a switch in which on movement of the parts in a switch closing direction the contact carried by the resilient blade engages a cooperating stationary contact and on further movement the blade is pressed back from the actuating arm which is also carried by the resilient blade for maintaining at least a minimum contact pressure.

Other objects will be apparent from the specification, claims and drawings in which Figure 1 is a view, partly in section, of a thermostat embodying the invention,

Figure 2 is a plan view, partly in section, of the device of Figure 1 but with the cover removed, and

Figure 3 is a view similar to Figure 1 but with the parts in a different operative position.

Referring to the three figures of the drawing, I have illustrated my invention in connection with a thermostat having a base 12 of insulating material to which is suitably secured a metal bracket l4 provided with a terminal extension l6 that carries a binding screw l1. The bracket 14 also has a pair of upstanding cars 19 and 20 that carry a pin 22 on which is pivoted a bracket 25 to which a U-shaped bimetal element 21 is suitably secured. The U-shaped bimetal element 21 has an upper leg 28 that serves to actuate a switching mechanism to be described later and a lower leg 29 that is positioned by a cam 31 having a helical cam surface 32 against which the leg 29 of the bimetal element 21 is biased as well be described. The cam 31 is adjusted by turning a knob 35 secured on the upper end of a rod 36 that is suitably secured to and pivotally mounted in the base 12. The knob 35 may be provided with suitable indicia cooperating with markings on a cover 38 that is also suitably secured to the base l2. It will be seen that turning the cam 31 in a clockwise direction as seen in Figure 2 will lower the leg 29 of the bimetal element 21.

The bracket 14 is also provided with an up- 2 standing portion 40 having its upper extremity 4| bent to lie generally parallel to the base 12. A resilient blade 43 is suitably secured to the extremity 4| of the bracket l4 and also lies generally parallel to the base 12. A rigid steel switch actuating member 41 is secured to the blade 43 adjacent the extremity 4| of the bracket I4. A short portion 45 of the blade 43 lies between the member 41 and the extremity 41 of the bracket 14. The actuating member 41 extends generally parallel to the blade 43 but at the left-hand end thereof the member 41 has an ofi'set portion 48 that engages the lower surface of the blade 43. The blade 43 has a relatively narrow and long and therefore relatively flexible portion 46 extending between the point of attachment of the member 41 to the blade 43 and the offset portion 48. The member 41 is so formed that the blade 43 presses lightly against the member 41 at the offset portion 48.

The member 41 is provided with a pair of upstanding ears 51 at offset portion 48 that are bent over to form an abutment for the extremity of the upper leg 28 of the bimetal element 21.

A movable contact 56 is secured to the lefthand extremity of the blade 43 by means of a reduced portion 51 extending through an aperture in member 41. The contact 56 is of greater diameter than the aperture in the. member 41. The contact 55 cooperates with a stationary contact 58 carried on the upper end of a screw 60 that is screw-threaded in a terminal strip 52 that is suitably attached to the base l2. The screw 60 is provided with a hexagonal portion 84 for adjusting the height of the contact 58. The terminal strip 62 may be provided with a suitable binding screw 85.

A magnet 68 is secured to the base 12 in cooperative relation with the member 41. The portion of the member 41 adjacent the magnet serves as an armature.

Operation The extremity 4| of the bracket 14 so carries the resilient blade 43 that the member 41 normally is in a position close enough to the magnet 58 to enable the magnet to pull the member 41 downwardly and cause engagement of the movable contact 56 with the stationary contact 58. The magnetic attraction is also strong enough to cause the portion 46 of the blade 43 to be pressed back with respect to the member 41 until the back of the contact 56 engages the offset portion 48 of the member 41 as shown in Figure 3. The adjusted position of the stationary contact 58 thus determines the minimum distance between the member 41 and the magnet 88.

If the parts of the thermostat are in the position shown in Figure 3 and the temperature should change to cause the bimetal element 21 to vary and push downwardly on the cam surfa e then the pper leg 24 will exert a force in an upwardly direction on the abutment oi the member 41 formed by the ears I. When sumcient force is-built up in the bimetal the attraction of the magnet ll for the member 41 will be overcome and the memberwill move suddenly to a position as shown in Figure 1, separating contacts 56-".

Likewise on an opposite temperature change the bimetal element 21 will permit the member 41 to move downwardly until the attraction of the magnet 88 tor the member 41 overcomes the upwardly applied force supplied by the bimetal element 21 to snap the member 41 to the position shown in Figure 3.

The operating differential of the thermostat is determined by the minimum distance between the member 41 and the magnet SI and this distance may be adjusted by turning the screw 6. that carries stationary contact II.

It will be noted that whenever the contacts 5H0 are in engagement, except for transitory conditions, the minimum contact pressure is determined by the force necessary to press the blade 43 back from the member 41 at oiiset portion 48 to the position in which contact 6 abuts the portion 48 of member 41. Thus it will be seen that the blade 43 serves the dual'purpose oi acting as a pivotal support for the member 41 and as a resilient pressback contact carrying blade.

While the invention has been'described in connection with a thermostat having a bimetal sensing element it will be evident that the switch structure could be used for other purposes provided an actuating element of suiiicient resiliency to permit snap action of the contacts is employed. I

Various modifications of the invention will be apparent to those.skilled in the art and it is intended that the scope of the invention is to be limited only by .the appended claims.

1. In a snap switch, a base, a substantially flat resilient blade fixed at one end to said base, a movable contact onsaid blade, a contact actuating arm attached to said blade intermediate said contact and the point atwhich said blade is fixed to said base, said blade serving to pivotally carry said arm on said base, an extension on said arm limiting movements or said contact with respect thereto, a cooperating contact on said base, and snap acting means carried on said base and acting on said arm for causing snap movement of said arm and said movable contact.

2. In an electric switch, in combination, a base, a substantially flat resilient blade rigidly mounted at one "end on said base, a movable contact on the other end oi. said blade, a cooperating stationary contact on said base, a rigid member carried by said blade adJacent its attachment to said base, said member also normally engaging said blade at a point adjacent, said contacts but adapted to be separated therefrom when said contacts are in engagement, means acting between said member and said base causing snap movement of said movable contact and an actuating element including a resilient portion for moving said member to actuate said movable contact. v I

3. In a condition responsive switch, in combination, a base, a substantially flat resilient blade rigidly mounted at one end on said base, a

and said member for actuating said movable contact.

4. In a thermostatic switch, in combination, a base, a substantially flat resilient blade rigidly mounted at one end on said base, a movable contact on the other end of said blade, a cooperating stationary contact on said base, a rigid member carried by said blade adjacent its attachment to said base, said member also normally engaging said blade at a point adjacent said contacts but adapted to be separated therefrom when said contacts are in engagement, a magnet carried by said base and acting on said member to bias said contacts to closed position, and a bimetal element carried by said base and adapted to bias said member in a direction to overcome the bias of said magnet to separate said contacts.

5. In an electric switch, in combination, a base, a resilient blade fixed to said base, a movable contact on said blade, a cooperating stationary contact on said base, a rigidmember mounted on said blade intermediate said movable contact and the point at which said blade is attached to said base, said member also normally engaging said blade at a point adjacent said contacts but adapted to be separated therefrom when said contacts are in engagement, means acting between said member and said base causing snap movement oi at one end on said base. a movable contact on the other end of said blade, a cooperating stationary contact on said base, a rigid member carried by said blade adjacent its attachment to said base, said memberalso normally engaging said blade at a point adjacent'said contacts but adapted to be separated therefrom when said contacts are in engagement, 'said member and the contact carrying portion of said blade being pivotally mounted on said base on an axis determined by the portion of said blade intermediate said member and said base; means acting between said member and said base causing snap movement of said contacts, and an actuating element having a resilient portion acting on said member to rotate said member about said axis.

. CARL G. momma-m. REFERENCES CITED The following references are of record in the file of this patent: v

UNITED STATES PATENTS 

